1. Field of the Invention
This invention relates to a fixing structure for a mounting member such as a dustproof seal mounted on a nut for a ball screw or the like.
2. Related Background Art
For example, in the case of a ball screw often used in a machine tool, if during operation, foreign substances such as cutting scraps and cutting oil adhere to the screw shaft and come into a nut, the wear of balls or a spiral groove surface which is the rolling surface of the balls may abnormally increase or the ball screw may become bad in operation to thereby reduce the service life of the ball screw, and further may result in damage to the ball screw. To prevent this, it is usually practiced to fixedly mount a dustproof seal on a ball screw nut.
As a prior-art fixing structure for a seal to a ball screw nut, there is known one as shown, for example, in FIG. 15 now to be described. To facilitate understanding, suffixes "R" and "L" have been used in the reference numbers to denote (R)ight-hand and (L)eft-hand portions of the assembly. This structure has seal mounting stepped portions 3L and 3R of a large diameter on the left and right end portions of a ball screw nut 2 screwed onto a ball screw shaft 1 through balls B, and threaded holes 4R and 4L are formed in the circumferential surfaces of the stepped portions 3R and 3L. That is, there is formed one or two radial threaded holes 4R, 4L extending from the right portion of the outer peripheral surface 2b of the ball screw nut 2 and the flanged peripheral surface 2f of the ball screw nut 2 to the respective stepped portions 3R and 3L. The depth (width) of the stepped portions is made equal to the width L of the corresponding seals 5, and seals R and 5L are fitted to the stepped portions 3R and 3L, respectively, whereafter set screws 6R and 6L threadably engaged with the threaded holes 4R and 4L, respectively, are fastened, whereby the seals 5R and 5L are fixed in the circumferential direction and the axial direction.
In the prior-art fixing structure for the seal to the nut shown in FIG. 15, the seals 5R and 5L are fixed by the set screws 6R and 6L threadably engaged with the threaded holes 4R and 4L and therefore, it is necessary to form the threaded holes 4R and 4L in the ball screw nut 2. Thus, working processes such as tap prepared hole formation and tapping work are required. Further, to ensure the seals 5R and 5L are to be fixed reliably, when threaded holes are formed at two locations in the circumferential direction, there has been a problem that more time and labor are required for working and it is difficult to improve productivity.